Poly(esterurethane) coating cured with an aminoplast on a solid substrate

ABSTRACT

Cured coatings having a high degree of extensibility and other desirable properties are obtained from compositions comprising a hydroxyl-containing, urethane reaction product containing a polyester component and an amine-aldehyde resin. Preferred compositions contain a polymeric polyol of low glass transition temperature. These compositions are storage-stable in one package, and the cured coatings are adherent, durable and highly extensible. These coatings are particularly useful on resilient and rubbery substrates, such as foam rubber, polyurethane foam and vinyl foam, and on soft metal surfaces such as mild steel and aluminum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Serial No.347,022, filed April 2, 1973, now abandoned, and is being filed pursuantto a restriction requirement in said application. Application Serial No.347,022, in turn, is a continuation of application Serial No. 828,337,filed May 27, 1969, now abandoned. Application Ser. No. 567,219 filedApr. 11, 1975 is a continuation-in-part of application Ser. 347,022.

BACKGROUND OF THE INVENTION

Recent advances in coating technology have provided coatings which aresuitable for use over various substrates which are difficult to coat andhaving many different problems. Coatings of excellent appearance, a highorder of durability and having the ability to withstand severeenvironmental conditions have been obtained. Among the more advancedcoatings are those employed on vehicles, such as automobiles, where goodappearance must be maintained over long periods despite exposure toweather and various forms of attack during use.

Recently, there has been interest in the use of rubbery, resilientmaterials for areas which are subject to mechanical shock such asautomobile bumpers and moldings, exposed corners and surfaces ofindustrial machines, kickplates and other areas of doors and entrances,and the like. The use of such materials aids in providing protectionagainst permanent structural damage, but in order to attain the desiredappearance a decorative and protective coating must be applied to thesurface and this coating can also be applied to the surface and thiscoating can also be damaged during use. Conventional coatings, includingthose employed on rubber and similar extensible objects heretofore, donot have the required combination of properties. These necessaryproperties include:

1. Extensibility - This property is necessary in order that theadvantages of the resilient substrate can be utilized withoutdestruction of the integrity of the surface of the coating.

2. Tensile Strength - A high degree of tensile strength is alsonecessary in order to avoid rupture of the film during use.

3. Package Stability - In order to permit ease of application, theliquid coating composition should be stable for extended periods underambient conditions without either gelation or depolymerization of theresin contained therein.

4. Film stability - Certain coatings which are extensible and which havea relatively high tensile strength lose these properties upon aging andparticularly if the coating is exposed to sunlight, weathering, etc.

5. Impact resistance - The coating should have adequate impactresistance at various temperatures as encountered in extreme weathervariations, including temperatures as low as -20°F. and as high as120°F.

6. Adhesion - The coating should have satisfactory adhesion to thevarious substrates with which it is to be employed including extensiblematerials such as foams, rubber and the like, and metals such as mildsteel. In addition the coatings should have satisfactory intercoatadhesion with succeeding coats or with various primers which can beemployed.

7. Chemical and Humidity Resistance - This includes properties such assaponification resistance upon exposure to acids and alkalis, resistanceto various solvents and resistance to atmospheres of high humidity andheat.

8. Resistance to Cracking under Temperature-Humidity Cycling - Thisproperty is important where the coating might be exposed to rapidvariations in temperature and humidity as might be encountered byautomobiles during travel or storage. This property is tested bysuccessively exposing the coated object to conditions of hightemperature and high humidity alternated with exposure to lowtemperature and low humidity.

Still other properties which are important for commercial applicabilityinclude sprayability at reasonable solids contents, non-toxicity, andlow sensitivity to moisture.

It is especially difficult to obtain the above properties in combinationsince, in most instances, the obtention of one or several of theproperties desired requires the use of materials and formulations whichunder ordinary circumstances tend to make the other desired propertiesless satisfactory.

SUMMARY OF THE INVENTION

The compositions of the present invention comprise (1) an ungelled,hydroxyl-containing urethane reaction product of an organicpolyisocyanate and a polyhydric material comprising a major proportionof a substantially linear polyester, and (2) an amine-aldehyde resin.The polyester is formed from an alcohol component having an averagefunctionality of at least about 1.9 and an acid component consistingessentially of one or more monomeric carboxylic acids or anhydridescontaining 2 to 14 carbon atoms and also having an average functionalityof at least about 1.9. To obtain the desired extensibility and otherproperties, the alcohols and acids or anhydrides used should contain atotal of not more than about one gram-mole of compounds having afunctionality of 3 or more per 500 grams of the total of the alcoholsand acid or anhydride employed.

Such coatings can be applied to virtually any solid substrate and areespecially useful on rubbery, resilient substrates such as polyurethaneor polyethylene foam, natural or synthetic rubber or rubber foam, andvarious elastomeric plastic materials. They are also particularly usefulon other substrates such as mild steel or aluminum.

These compositions, although based on a urethane system, aredistinguished from ordinary polyurethanes because they are bothstorage-stable in one package and yet form a cross-linked thermosetcured coating.

The coatings herein provide all the above-mentioned properties to asatisfactory degree and have a combination of these properties notheretofore considered possible.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of the invention contain as one component anisocyanate-modified resin containing hydroxyl groups and formed byreacting a polyhydric material comprising a substantially linearpolyester polyol with an organic polyisocyanate. The isocyanate-modifiedresin is combined with an aminoplast resin to provide the coatingcomposition of the invention.

It is necessary that the polyester polyol employed have certainproperties in order to provide a coating of the desired characteristics.These properties are obtained in general by utilizing a polyestercontaining a polyol component having an average functionality of atleast about 1.9. The polyol component in most cases consists essentiallyof one or more diols with up to about 25 mole percent of polyols presenthaving 3 or more hydroxyl groups. While it is not always necessary tohave a triol or higher polyol present, some branching is desirable,although the polyester should not be highly branched. There may also bepresent a small amount of monoalcohol, particulary if larger proportionsof higher polyols are used. In certain instances, such as where veryhigh molecular weight polyols are used, the polyols can be largely oreven entirely made up of compounds of functionality higher than two.

The diols which are usually employed in making the polyester includealkylene glycols, such as ethylene glycol, propylene glycol, butyleneglycol, and neopentyl glycol, and other glycols such as hydrogenatedbisphenol A, cyclohexane dimethanol, caprolactone diol (i.e., thereaction product of caprolactone and ethylene glycol). hydroxyalkylatedbisphenols, polyether glycols, e.g. poly(oxytetramethylene) glycol, andthe like. However, other diols of various types and, as indicated,polyols of higher functionality can also be utilized. Such higherpolyols can include, for example, trimethylolpropane, trimethylolethane,pentaerythritol, and the like, as well as higher molecular weightpolyols such as those produced by oxyalkylating low molecular weightpolyols. An example of such a higher molecular weight polyol is thereaction product of 20 moles of ethylene oxide per mole oftrimethylolpropane.

The acid component of the polyester consists essentially of monomericcarboxylic acids or anhydrides having 2 to 14 carbon atoms per molecule.The acids should have an average functionality of at least about 1.9;the acid component in most instances contains at least about 75 molepercent of dicarboxylic acids or anhydrides. The functionality of theacid component is based upon considerations similar to those discussedabove in connection with the alcohol component, the total functionalityof the system being kept in mind.

Among the acids which are useful are phthalic acid, isophthalic acid,terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid,adipic acid, azelaic acid, sebacic acid, malic acid, glutaric acid,chlorendic acid, tetrachlorophthalic acid, and other dicarboxylic acidsof varying types. The polyester may include minor amounts of monobasicacid, such as benzoic acid, and also there can be employed higherpolycarboxylic acids, such as trimelletic acid and tricarballylic acid(where acids are referred to above, it is understood that the anhydridesof those acids which form anhydrides can be used in place of the acid).It is preferred that the polyester include an aliphatic dicarboxylicacid as at least part of the acid component.

Besides polyester polyols formed from polybasic acids and polyols,lactone polyesters can also be employed. These products are formed fromthe reaction of a lactone or mixture of lactones in which the lactonehas the following general formula: ##EQU1## in which n is at least 4, atleast n + 2R's are hydrogen, and the remaining R's are substituentsselected from the group consisting of hydrogen, alkyl, cycloalkyl,alkoxy and single ring aromatic hydrocarbon radicals; such asepsilon-caprolactone with a polyol or a hydroxy acid. Such products aredescribed in U.S. Pat. 3,169,945 to Hostettler et al.

As mentioned, the overall functionality per unit weight of the reactionsystem is important. There should not be present more than about onegram-mole of acids and/or alcohols having a functionality of 3 or more,per 500 grams of the total weight of these compounds. By "functionality"is meant the number of reactive hydroxyl and carboxyl groups permolecule, with anhydride groups being considered as equivalent to twocarboxyl groups. It can be noted that certain compounds contain bothhydroxyl and carboxyl groups; examples are 6-hydroxyhexanoic acid,8-hydroxyoctanoic acid, tartaric acid, etc.

The polyester is produced using conventional techniques, with thereaction conditions and the ratio of reactants chosen so as to provide aproduct having residual hydroxyl groups, i.e., a polyester polyol. Thenumber of hydroxyls present in the product can be varied, but it ispreferred that its hydroxyl value be at least about 30 and preferablymore than 80.

The polyester polyol as described provides the major proportion of thepolyhydric material and be the entire polyhydric component utilized.However, in many instances, other hydroxy-containing compounds are used,such as polyether polyols of the various types known in the art;monomeric polyols, especially diols, such as 1,4-butanediol, neopentylglycol, and the like; monohydric alcohols; and polyfunctional compoundscontaining one or more hydroxyls, such as ethanolamine.

The organic polyisocyanate which is reacted with the polyhydric materialas described is essentially any polyisocyanate, e.g. hydrocarbonpolyisocyanates or substituted hydrocarbon diisocyanates. Many suchorganic polyisocyanates are known in the art, including p-phenylenediisocyanate, biphenyl diisocyanate, toluene diisocyanate,3,3'dimethyl-4,4'biphenylene diisocyanate, 1,4-tetramethylenediisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexane-1,6diisocyanate, methylene bis(phenyl isocyanate), lysine diisocyanate,bis(isocyanatoethyl) fumarate, isophorone diisocyanate and methylcyclohexyl diisocyanate. There can also be employedisocyanate-terminated adducts of diols, such as ethylene glycol,1,4-butylene glycol, polyalkylene glycols, etc. These are formed byreacting more than one mole of a diisocyanate, such as those mentioned,with one mole of a diol to form a longer chain diisocyanate.Alternatively, the diol can be added along with the diisocyanate.

While diisocyanates are preferred, higher polyisocyanates can beutilized as part of the organic polyisocyanate. Examples are1,2,4-benzene triisocyanate and polymethylene polyphenyl isocyanate.

It is preferred to employ an aliphatic diisocyanate, since it has beenfound that these provide better color stability in the finished coating.Examples include bis(isocyanatocyclohexyl)methane, 1,4-butylenediisocyanate and methylcyclohexyl diisocyanate. The proportions of thediisocyanate and the polyester are chosen so as to provide ahydroxyl-containing product. This can be accomplished by utilizing aless than stoichiometric amount of polyisocyanate, i.e. less than oneisocyanate group per hydroxyl and carboxyl group in the polyester.Higher (e.g. stoichiometric or excess) isocyanate levels can be presentif the reaction is terminated at the desired stage, as by addition of acompound which reacts with the residual isocyanate groups; water,alcohols and amines are examples of such compounds.

In one especially desirable embodiment of the invention, apolyfunctional alcohol is used to terminate the reaction at the desiredstage (determined by the viscosity), thereby also contributing residualhydroxyl groups. Particularly desirable for such purposes areaminoalcohols, such as ethanolamine, diethanolamine and the like, sincethe amino groups preferentially react with the isocyanate groupspresent. Polyols, such as ethylene glycol, trimethylolpropane andhydroxyl-terminated polyesters, can also be employed in this manner.

While the ratios of the components of the polyester, the polyisocyanateand any terminating or blocking agent can be varied, it will be noted bythose skilled in the art that the amounts should be chosen so as toavoid gellation and to produce an ungelled, urethane reaction productcontaining hydroxyl groups. The hydroxyl value of the urethane reactionproduct should be at least 10 and preferably 10 to about 200.

The urethane reaction product as described above is mixed with anaminoplast resin to provide the coating composition. Aminoplast resinsare aldehyde condensation products of melamine, urea, and similarcompounds; products obtained from the reaction of formaldehyde withmelamine, urea or benzoguanamine are most common and are preferredherein. However, condensation products of other amines and amides canalso be employed, for example, aldehyde condensates of triazines,diazines, triazoles, guanidines, guanamines and alkyl and arylsubstituted derivatives of such compounds, including alkyl and arylsubstituted ureas and alkyl and aryl substituted melamines. Someexamples of such compounds are N,N'-dimethylurea, benzourea,dicyandiamide, formoguanamine, acetoguanamine, ammeline,2-chloro-4,6-diamino-1,3,5-triazine,6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole,triaminopyrimidine, 2-mercapto-4,6-diaminopyrmidine, 2,4,6-triethyltriamino-1,3,5-triazine, and the like.

While the aldehyde employed is most often formaldehyde, other similarcondensation products can be made from other aldehydes, such asacetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural, andothers.

The amine-aldehyde condensation products contain methylol or similaralkylol groups, and in most instances at least a portion of thesealkylol groups are etherified by a reaction with an alcohol to provideorganic solvent-soluble resins. Any monohydric alcohol can be employedfor this purpose, including such alcohols as methanol, ethanol,propanol, butanol, pentanol, hexanol, hepanol and others, as well asbenzyl alcohol and other aromatic alcohols, cyclic alcohol such ascyclohexanol, monoethers of glycols such as Cellosolves and Carbitols,and halogen-substituted or other substituted alcohols, such as3-chloropropanol. The preferred amine-aldehyde resins are etherifiedwith methanol or butanol.

For optimum properties, it is preferred to include in the composition apolymeric polyol having a low glass transition temperature, i.e., havinga glass transition temperature below about 25°C. The inclusion of such apolymeric polyol gives a balance of flexibility and hardness. Among thepreferred polymeric polyols are polyether polyols; especially preferredare poly(oxyalkylene) glycols such as polyethylene glycol, polypropyleneglycol, and other such glycols having up to about 6 carbon atomsseparating each pair of oxygen atoms. A specific preferred polyol ispoly(oxytetramethylene)glycol. Other highly desirable polymeric polyolsare polyester polyols having the desired glass transition temperature,especially those produced from acyclic reactants such as adipic acid andazelaic acid and alkylene glycols; poly(neopentyl adipate) is a usefulexample. Still other polymeric polyols of suitable properties includecondensates of lactones with polyols, such as the product fromcaprolactone and ethylene glycol, propylene glycol, trimethylolpropane,etc.

The polymeric polyol can be incorporated into the composition in variousways. In some instances the polyester polyol employed can serve as thepolymeric polyol, but this does not usually provide a coating ofsuitable hardness. More usually, the "soft" polymeric polyol is used inconjunction with a polyester polyol (or constituent thereof) having ahigher glass transition temperature. One method is to include thepolymeric polyol in the polyester as part of the polyol component;another way is to produce an isocyanato-terminated adduct or prepolymerfrom the polymeric polyol and the polyisocyanate; a third method is toblend the polymeric polyol as such with the polyester, before or afterthe polyester is reacted with the polyisocyanate. The choice of methoddepends upon the particular components used and the properties desired,but in each instance the product contains both "hard" and "soft"segments in a type of block copolymer.

The proportions of the above components can be varied to provide certainproperties. For example, higher levels of polymeric polyol result insomewhat softer and more extensible coatings, whereas harder, moreresistant coatings are obtained by increasing the proportion ofaminoplast resin. The amounts employed depend in large part upon thenature of the particular components, e.g., the specific polyester,aminoplast resin, as well as the type of polymeric polyol, if any,employed. In most cases the overall composition contains from about 50to about 95 percent by weight of urethane reaction product, and fromabout 5 to about 50 percent of aminoplast resin. The preferredcompositions in which a polymeric polyol is included contain from about45 to about 90 percent by weight of urethane reaction product, fromabout 5 to about 40 percent by weight of aminoplast resin, and fromabout 2 to about 20 percent by weight of polymeric polyol. Thepolyurethanes described above can be made water-dispersible by theincorporation of salt groups into the polymer backbone. For example, thepolyurethane can be prepared with unreacted acid groups and the acidgroups neutralized. Alternately, the polyurethane could be prepared withbasic tertiary amino groups which could be neutralized with acid orquaternized.

In addition to the components above, the compositions ordinarily containother optional ingredients, including various pigments; any of thepigments ordinarily utilized in coatings of this general class can beused. In addition, various fillers, plasticizers, antioxidants, flowcontrol agents, surfactants and other such formulating additives areemployed in many instances. The composition is ordinarily contained in asolvent, which can be any solvent or solvent mixture in which thematerials employed are compatible and soluble to the desired extent.

The compositions herein can be applied by any conventional method,including brushing, dipping, flow coating, etc., but they are most oftenapplied by spraying. Usual spray techniques and equipment are utilized.They can be applied over virtually any substrate, including wood,metals, glass, cloth, plastics, foams, and the like, as well as overvarious primers.

The coatings are cured at elevated temperatures. In most cases the cureschedule is from about 20 to about 40 minutes at 140°F. to 260°F. Higheror lower temperatures with correspondingly shorter and lower times canbe utilized, although the exact cure schedule best employed depends inpart upon the nature of the substrate as well as the particularcomponents of the composition. Acid catalysts and other curing catalystscan be added to aid in curing if desired; these can permit the use oflower temperatures and/or shorter times.

The invention will be further described in connection with severalexamples which follow. These examples are given as illustrative of theinvention and are not to be construed as limiting it to their details.All parts and percentages in the examples and throughout thespecification are by weight unless otherwise indicated.

EXAMPLE 1

The following were charged to a reaction vessel:

                   Parts by Weight                                                ______________________________________                                        Neopentyl glycol 126.9                                                        Trimethylolpropane                                                                             22.1                                                         Adipic acid      72.3                                                         Isophthalic acid 123.2                                                        ______________________________________                                    

This mixture was heated to 200°C. for 30 minutes and then at 220°C.until the resin had a Gardner-Holdt viscosity of F (60 percent solids inmethyl ethyl ketone), and acid value of about 10 and a hydroxyl value ofabout 100. This polyester polyol was then mixed with the following:

                        Parts by Weight                                           ______________________________________                                        Polyester             70                                                      Methyl ethyl ketone   35                                                      Methane-bis(cyclohexyl isocyanate)*                                                                 7.13                                                    ______________________________________                                         *Mobay D-244   This mixture was heated at 150°F. for 20 hours and      then cooled to 120°F. for 3 more hours. There were then added 22     parts of n-butanol and 0.3 part of ethanolamine. The product had a     Gardner-Holdt viscosity of Z1-Z2, a non-volatile solids content of about     60 percent and an acid value of 3.7.

A gray coating composition was formulated using the urethane reactionproduct thus produced by blending the following:

    ______________________________________                                                           Parts by Weight                                            ______________________________________                                        Urethane reaction product                                                                          196.5                                                    Hexakis(methoxymethyl)melamine                                                ("Cymel 301")        18.7                                                     Poly(oxytetramethylene) glycol                                                                     15.8                                                     CAB solution*        7.5                                                      Pigment paste        67.5                                                     Toluene              217.5                                                    Cellosolve acetate   49.5                                                     Ethyl Cellosolve     99                                                       Diacetone alcohol    74.5                                                     p-Toluene sulfonic acid                                                                            1.5                                                      ______________________________________                                         *20 percent solution of 1/2 second cellulose acetate butyrate in 80/20        toluene/ethanol?                                                         

The pigment paste employed was ground in a solution of a polyester madefrom 146 parts of neopentyl glycol, 112 parts of adipic acid, 191 partsof isophthalic acid and 103 parts of trimethylolpropane; the paste wasproduced by mixing the following:

                       Parts by Weight                                            ______________________________________                                        Polyester (60 percent solids                                                  in xylene)           89                                                       TiO.sub.2            260                                                      Molacco black        13                                                       Xylene               28                                                       Methyl isobutyl ketone                                                                             43.5                                                     Butanol              10.5                                                     ______________________________________                                    

This mixture was ground in a ball mill until the particles had afineness of 61/2 Hegman and then 50 parts of toluene were added.

The coating composition thus obtained had good storage stability andexcellent properties. For example, when baked at 250°F. for 60 minutesit provided a film having outstanding extensibility (maximum elongation181 percent) and tensile strength (2.09 × 10⁵ g/cm², measured on InstronTester). When coated on polyurethane foam of the type employed forautomobile bumpers (having a density of 40 pounds per cubic foot and aShore "A" hardness of 78), it had desirable properties, including impactresistance in excess of 160 inch/lbs (measured on a Gardner VariableImpact Tester). This composition is suitable as a primer over such foamsand similar materials.

EXAMPLE 2

A white coating composition was produced using the urethane reactionproduct described in Example 1 and a pigment paste made in a mannersimilar to that described in Example 1 but without carbon black; thepigment contained 61.5 percent TiO₂ and 12 percent of polyester alongwith suitable solvents. The coating composition had the followingconstituents:

                       Parts by Weight                                            ______________________________________                                        Urethane reaction product                                                                          74                                                       Hexakis(methoxymethyl)melamine                                                ("Cymel 301")        10                                                       Pigment paste        40                                                       Poly(oxytetramethylene glycol)                                                (mol. wt. 1000)      6                                                        CAB solution (as in Example 1)                                                                     5                                                        p-Toluene sulfonic acid                                                                            0.5                                                      Methyl ethyl ketone  100                                                      Cellosolve acetate   50                                                       ______________________________________                                    

Films of this composition (baked 60 minutes at 250°F.) had a maximumelongation of 177 percent and tensile strength of 1.55 × 10⁵ g/cm². Whencoated over the primed foam produced in Example 1, it provided a coatedproduct of outstanding properties including good impact resistance.

EXAMPLE 3

A coating composition was produced as in Example 1 except that theaminoplast resin utilized was a more resinous, less highly methylatedmelamine-formaldehyde resin known as "QR-483". The product hadproperties substantially similar to that from Example 1.

EXAMPLE 4

Following the procedure of Example 1, a coating composition was producedusing the urethane reaction product and pigment paste described therein,but with a butylated melamine-formaldehyde resin made using 5.5 moles offormaldehyde and 6 moles of butanol per mole of melamine; the resin wasa 60 percent solids solution in 25/75 butanol/xylene. The coatingcomposition contained the following:

                       Parts by Weight                                            ______________________________________                                        Urethane reaction product                                                                          110                                                      Butylated melamine resin                                                                           42                                                       Poly(oxytetramethylene)glycol                                                 (mol. wt. 1000)      10.5                                                     Pigment paste        45                                                       CAB solution (as in Example 1)                                                                     5                                                        Xylene               130                                                      Cellosolve acetate   40                                                       Ethyl Cellosolve     80                                                       Diacetone alcohol    50                                                       p-Toluene sulfonic acid                                                                            2                                                        ______________________________________                                         This composition produced extensible films of somewhat lower maximum     elongation than those above but with good tensile strength (2.65 ×     10.sup.5 g/cm.sup.2). When coated over foam as in Example 1, the coating     had good impact resistance and other properties.

EXAMPLE 5

A polyester containing poly(oxytetramethylene)glycol in the polyestermolecule was produced from the following:

                       Parts by Weight                                            ______________________________________                                        Neopentyl glycol     4875                                                     Adipic acid          3014                                                     Isophthalic acid     5132                                                     Trimethylolpropane   921                                                      Poly(oxytetramethylene glycol)                                                                     3750                                                     (mo. wt. 1000)                                                                ______________________________________                                    

The polyester produced had an acid value of 5.9 and a hydroxyl value of59. It was reacted with the following:

                       Parts by Weight                                            ______________________________________                                        Polyester            1800                                                     Methyl isobutyl ketone                                                                             1080                                                     Methane-bis(cyclohexyl isocyanate)*                                                                168                                                      ______________________________________                                         *"Hylene W                                                               

This mixture was heated at 150°F. for 61/2 hours; to 2605 parts of theproduct there were added 3.9 parts of ethanolamine and 520 parts ofbutanol. The product had a Gardner-Holdt viscosity of Z3 and contained51.2 percent non-volatile solids. This urethane reaction product wasformulated into a coating composition as follows:

                       Parts by Weight                                            ______________________________________                                        Urethane reaction product                                                                          76                                                       Hexakis(methoxymethyl)melamine                                                ("Cymel 301")        7.5                                                      Pigment paste (as in Example 2)                                                                    37                                                       CAB solution (as in Example 1)                                                                     5                                                        Cellosolve acetate   60                                                       Methyl ethyl ketone  30                                                       Toluene              80                                                       p-Toluene sulfonic acid                                                                            0.75                                                     ______________________________________                                    

Films of this composition, baked 30 minutes at 250°F. had excellentextensibility (187 percent maximum elongation) and tensile strength(1.86 × 10⁵ g/cm²). When employed as a topcoat (as in Example 2)coatings of good overall properties were obtained.

In a similar manner, coating compositions of desirable properties areproduced using other polyesters of the class described, as well as otherpolyisocyanates, such as toluene diisocyanate, in place of thepolyesters and polyisocyanates in the examples. Also, while the examplesshow the inclusion of poly(oxytetramethylene)glycol, other polymericpolyols having low glass transition temperatures can be used instead;such polyols include, for instance, other polyether polyols and thepolyester polyols as described. Furthermore, while the inclusion of sucha polyol is usually desirable for obtention of properties as described,it can be omitted where a lesser degree of extensibility is required.

EXAMPLE 6

A water-dilutable, hydroxyl-containing urethane reaction product wasprepared according to the invention as follows:

To a clean reaction vessel under a nitrogen blanket were charged thefollowing:

                       Parts by Weight                                            ______________________________________                                        Polyester diol.sup.1 4690                                                     4,4'-Bis-(cyclohexyl isocyanate)                                              (HYLENE W)           2645                                                     Methyl-n-butyl ketone                                                                              2000                                                     Dibutyltin dilaurate 0.08                                                     ______________________________________                                         .sup.1 2345 parts of polycaprolactone diol (1250 molecular weight)            prepared from reaction of epsilon-caprolactone with diethylene glycol,        commercially available from Union Carbide Corporation as PCP 0230, and        2345 parts of 1,6-hexanediol adipate (1000 molecular weight) commercially     available from Witco Chemical Company as FORMREZ L4-55.                  

The mixture was stirred and heated at 110°C. for 1 hour, at which timethe following were added:

                       Parts by Weight                                            ______________________________________                                        Ester of neopentyl glycol and                                                 hydroxypivalic acid                                                           (Ester Diol 204)     410                                                      Trimethylol propane  361                                                      Dimethylol propionic acid                                                                          281                                                      Methyl-n-butyl ketone                                                                              267                                                      Methyl isobutyl ketone                                                                             194                                                      ______________________________________                                    

The reaction mixture was heated to 100°C. and after two hours at 100°C.,90 parts by weight of HYLENE W and 38 parts by weight of triethylenediamine were added. The resin was kept at 90°C. until a Gardnerviscosity of 70-80 seconds is reached, when the reaction was terminatedby the addition of 46.5 parts of monoethanolamine and 264.5 parts ofpolycaprolactone triol (PCP 0301) having a molecular weight of 300 andprepared from ring opening epsilon-caprolactone with trimethylolpropane.

The mixture was held at 90°C. for 30 minutes and 98.5 parts ofhydroxyethyl ethylene imine were added and the temperature raised to100°C. and held for one hour. Finally, 21.08 parts by weight ofisopropyl alcohol and 702 parts by weight of n-butyl alcohol were addedto thin the reaction mixture. The final resinous product had an acidvalue of 3.6, an OH value of 73.2 (at 100 percent total solids), asolids content of 47.1 percent, and a Gardner-Holdt viscosity of Y-Z.

The urethane reaction product prepared as described above was thenemployed in a water-dispersed coating composition by first neutralizingby mixing 10,000 parts of the urethane reaction product with 38 parts ofdimethyl ethanolamine and 3000 parts of distilled water (80 percent ofthe total theoretical neutralization). The aqueous dispersion was thensteam distilled to remove the organic solvent. The resultant dispersionhad an acid value of 4.2, a pH of 8.47 and contained 38.7 percent totalsolids. The Brookfield viscosity of the material at 23°C. and 20revolutions per minute was 2800 centipoises and at 23°C. and 100revolutions per minute was 1200 centipoises.

Twenty-five (25) percent by weight (total resin solids) of a methylatedmelamine-formaldehyde curing agent (sold commercially by Rohm and Haasas MM83) was added to the water-dispersed urethane reaction productprepared as described above to form a crosslinkable coating composition.The composition was deposited as a film on a cold rolled steel panel bydrawing down with a 3-mil draw bar and cured at 250°F. for 30 minutes toproduce a crosslinked coating which had excellent impact resistance,extensibility and tensile strength. The impact resistance was greaterthan 160 inch-pounds as measured on a Gardner Variable Impact Tester.The crosslinked film had a maximum elongation of 185 percent and tensilestrength of 3000 psi.

EXAMPLE 7

A water-dilutable poly(ester-urethane) polyol was prepared according tothe invention as follows:

A polyester diol was prepared from the following charge:

                       Parts by Weight                                            ______________________________________                                        Neopentyl glycol     6912                                                     Adipic acid          3936                                                     Trimethylol propane  1207                                                     Isophthalic acid (95 percent purity)                                                               6720                                                     Dibutyltin oxide     169                                                      ______________________________________                                    

The ingredients were heated, first to about 150°C. to initiate reaction,and as reaction continued under a nitrogen sparge to help remove water,the temperature was raised to about 210°C. to remove water. Theresultant polyester had an acid value of 21.5, a hydroxyl value (at 100percent total solids) of 85.4 and contained 98.7 percent total solids.

To a clean reaction vessel under a nitrogen blanket was charged thefollowing:

                       Parts by Weight                                            ______________________________________                                        Polyester diol (prepared above)                                                                    700                                                      Methyl ethyl ketone  400                                                      4,4'-Bis-(cyclohexyl isocyanate)                                              (HYLENE W)           1038                                                     Methyl ethyl ketone  300                                                      ______________________________________                                    

The charge was heated to 65°C. and reaction continued for about threehours until a Gardner-Holdt viscosity of 40.0 seconds was reached, atwhich time the reaction was terminated by adding 55 parts ofmonoethanolamine, 795 parts of isopropyl alcohol and 285 parts ofn-butyl alcohol. After cooling to room temperature, the resultantproduct had an acid value of 11.5, a Gardner-Holdt viscosity of Y andcontained 60.6 percent total solids.

The urethane reaction product prepared as described above wasneutralized with dimethyl ethanolamine and dispersed in water by mixing10,400 parts of the urethane reaction product with 145 parts of dimethylethanolamine in 2000 parts of deionized water. After steam distillationto remove organic solvent, the resultant neutralized dispersed urethanereaction product had an acid value of 8.6, a pH of 8.4 and contained39.3 percent total solids. The material had a Brookfield viscosity at23°C. and 20 revolutions per minute of 1000 centipoises and at 23°C. and100 revolutions per minute a viscosity of 4000 centipoises.

Twenty-five (25) percent by weight (total resin solids) of a methylatedmelamine-formaldehyde curing agent MM83) was added to thewater-dispersed urethane reaction product prepared as described above toform a crosslinkable coating composition which is stable for over sixmonths at ambient temperature. The composition was deposited as a filmon a cold rolled steel panel by drawing down with a 3-mil draw bar. Thefilm was cured at 250°F. for 30 minutes to produce a crosslinked, hard,flexible coating which had a Sward Hardness of 46 and a Gardner impactresistance of greater than 160 inch-pounds as measured on a GardnerVariable Impact Tester.

According to the provisions of the patent statutes, there are describedabove the invention and what are now considered to be its bestembodiments. However, within the scope of the appended claims, it is tobe understood that the invention can be practiced otherwise than asspecifically described.

We claim:
 1. A coated article comprising a solid substrate havingthereon a cured coating comprising the reaction product of:A. anungelled hydroxyl-containing urethane reaction product of an organicpolyisocyanate and a polyhydric material, wherein a major portion ofsaid polyhydric material is a saturated polyester polyol; said polyesterpolyol being selected from the class consisting of:1. condensates ofi.an alcohol component having an average functionality of at least about1.9, and ii. a saturated acid component consisting essentially of 1 ormore monomeric carboxylic acids or anhydrides having 2 to 14 carbonatoms per molecule, said component having an average functionality of atleast about 1.9; and
 2. a lactone-polyester formed from reactinglactones or mixtures of lactones in which the lactone has the followingstructural formula: ##EQU2## wherein n is at least 4, at least n + 2R'sare hydrogen, and the remaining R's are substituents selected from thegroup consisting of hydrogen, alkyl, cycloalkyl, alkoxy and single ringaromatic hydrocarbon radicals with a polyol or a hydroxy acid;saidpolyhydric material containing a total of not more than one gram-mole ofcompounds having a functionality of 3 or more per 500 grams ofpolyhydric material; said urethane reaction product having a hydroxylvalue of at least 10; and b. an amine-aldehyde condensate.
 2. The coatedarticle of claim 1 in which said substrate is a polyurethane foam. 3.The coated article of claim 1 in which said composition includes as anadditional component a polymeric polyol having a glass transitiontemperature below about 25°C.
 4. The coated article of claim 3 in whichsaid polymeric polyol is a poly(oxyalkylene)glycol.
 5. The coatedarticle of claim 4 in which said poly(oxyalkylene)glycol ispoly(oxytetramethylene)glycol.
 6. The coated article of claim 3 in whichsaid polymeric polyol is a polyester polyol.
 7. The coated article ofclaim 1 in which said aminealdehyde condensate is an alkylatedcondensation product of formaldehyde with melamine, urea, orbenzoguanamine.
 8. The coated article of claim 1 in which the lactone isepsilon-caprolactone.